Members of the British National Adhering Body of the IPA have been involved in establishing a new Cryostratigraphy Research Group jointly with the Quaternary Research Association. The CRG was established to promote interdisciplinary research among Quaternary scientists and geomorphologists concerned with periglaciation. The CRG is a fixed-term research group of the QRA, and is affiliated with the British IPA body.
Cryostratigraphy seeks to classify permafrost sequences on the basis of their contained ground ice. Variation in the nature and distribution of ground ice allows identification of cryostratigraphic units whose interpretation and dating may allow reconstruction of past geocryological environments. The British Pleistocene is characterized by repeated growth and decay of permafrost, which caused the formation of distinctive landforms and structures, and disturbed superfcial sediments and bedrock. The application of cryostratigraphy in Quaternary research requires integration of process studies in the modern permafrost zone with traditional Quaternary stratigraphic investigations.
The CRG will hold one or two meetings per year at key periglacial localities within Britain. During these meetings, leading periglacial scientists will be invited to present keynote talks. The first meeting will take place in West Wales, probably in autumn 1996. Details of meetings will be published in the Quaternary Newsletter and on the QRA Website (http://www2.tcd.ie/pcoxon/qra.html). Enquiries should be directed to Julian Murton, Department of Earth Sciences, University of Wales, P.O. Box 914, Cardiff CFl 3YE, UK; Tel: 44 1222 87 4830; Fax: 44 1222 87 4326; E-mail: [email protected]
A Periglacial Workshop affiliated with Britain's National Adhering Body took place on 13 December 1995 at the University of Durham during the 1995 Annual Meeting of the British Sedimentological Research Group. The workshop, convened by Julian Murton (Cardiff), comprised ten talks and seven posters, and was attended by about 25 people. The objectives were to promote discussion of current research and provide opportunities for future collaboration.
The workshop opened with a talk by Colin Ballantyne (St. Andrews) on aeolian and niveo-aeolian deposits on Scottish mountains. Colin presented evidence for a general model of aeolian sedimentation commencing during the early Holocene. During the past few centuries the aeolian sediments on some mountains have been subject to extensive (niveo) aeolian reworking because of opening of the vegetation mat. Continuing the aeolian theme, Mark Bateman (Sheffield) discussed structures of possible periglacial origin within the Late Devensian coversand of north Lincolnshire. Some structures at Caistor morphologically resemble involutions, and their stratigraphic position suggested to Ko van Huissteden (Free University, Amsterdam) a similarity with Weichselian Late Pleniglacial sediments in the Netherlands. The third talk, by Geoff Duller (Aberystwyth), evaluated whether the luminescence dating of glacial and periglacial sediments was fact or fantasy. Geoff reviewed experimental data testing the "full-bleach assumption of the TL and OSL methods, and concluded that the degree of bleaching is highly variable.
The next two talks concerned periglacial rivers. David Bridgland (Durham) presented a climatic model for river terrace formation during the Middle and Upper Pleistocene in southern England. The model, based on stratigraphic observations, has aggradation of fluvial sediments, both at the beginning and end of periglacial conditions, and downcutting during the intervening periglacial episode. A debate ensued as to the effects of sea level change on fluvial activity. Following this, Ko van Huissteden presented cryostratigraphic and 14C evidence for Weichselian floodplain aggradation in the Netherlands. In contrast to the Weichselian Early and Late Pleniglacial (OI stages 4 and 2), when continuous permafrost existed here, the Middle Pleniglacial (OI stage 3) was a time of alternating aggradation and degradation of permafrost. An important phase of degradation at approximately 38,000 years BP was associated with floodplain erosion.
Wishart Mitchell (Luton) presented results on studies of rock glaciers in the Himalayas. Based on reconnaissance mapping in the Lahul and Ladakh regions, he suggested that the rock glaciers have developed under drier conditions than those associated with glaciers in the high mountains. Other rock glaciers in the Indus valley and the upper part of Spiti are currently developing out of retreating valley cirque glaciers.
Nel Caine (visiting at Durham) discussed the hydrologic and geomorphic processes in a nivation hollow from the Colorado Front Range, USA. During a 14-year record of discharges from the basin, the yields of both clastic sediment and dissolved material have been low, with a denudation rate of only 0.005 mm/yr. The figure suggests that this part of the alpine landscape has hardly been modified during the Holocene. Infilling of hollows by clastic sediment is countered by geochemical denudation, and it is the latter which may therefore be important in maintaining the basin form.
Julia Branson (Southampton) reported on recent progress in the development of the Global Geocryological Database. The GGD will in time comprise linked data centers (in Boulder, Moscow, Lanzhou and Southampton) which are compiling data from regions of perennially and seasonally frozen ground. The objectives of the database are to advance studies of permafrost, cold regions engineering and environmental change.
David Evans (Glasgow) described buried glacier ice from Ellesmere Island, in the Canadian High Arctic, and considered its implications for the glacial geology and geomorphology of subpolar glaciers. Because the ice is buried by till or alluvium whose thickness may exceed that of the active layer, the ice may be preserved indefinitely under present climatic conditions. Thus glaciers readvancing over the buried ice may reactivate it, which may partly explain the occurrence of thick englacial debris bands.
The final talk, by Julian Murton (Cardiff), discussed the sediments and stratigraphy of thermokarst lake basins in the Mackenzie Delta area, western Canadian Arctic. Based on cryostratigraphic observations, three stages of deposition have been distinguished: 1) widespread thaw slumping transporting upland sediments into thermokarst lakes; 2) reduced slumping promoting reworking of sediment and suspension settling; and 3) lake drainage permitting gelifluction and accumulation of peat and aeolian sand. The 14C dates from some stage 1 sediments suggest a progradation rate of approximately 4 cm/yr.
The following posters were displayed:
- Periglacial trimlines and the upper limit of Devensian glaciation, outer Hebrides (Colin Ballantyne, St. Andrews)
- Sediment transport by periglacial processes-The gravity fall model revisited (Julia Branson, Southampton)
- Relict rockglaciers in the British Isles (Stephan Harrison, Coventry)
- The Mis Tor Rockglacier, Dartmoor (Stephan Harrison, Coventry; Ed Anderson, Middlesex; and Vanessa Winchester, Oxford)
- Rock glaciers in the Himalaya (Wishart Mitchell, Luton)
- Near-surface brecciation of chalk, Isle of Thanet, Kent: A comparison with ice-rich bedrocks (Julia Murton, Cardiff)
- Cambering and gulls in unconsolidated Quaternary sediments in East Anglia, UK (Colin Whiteman, Brighton)
The workshop promoted enthusiastic discussion of periglacial research and demonstrated the important contribution that such work can make to Quaternary science. This was particularly well illustrated by the studies of periglacial aeolian and fluvial sedimentation. In addition, the workshop drew attention to at least three important topics that merit further research: 1) Anglo-Dutch optical dating studies of late Weichselian/Devensian sediments to improve cryostratigraphic correlations and palaeoenvironmental reconstructions, 2) comparative studies of mid-latitude Pleistocene river terraces to test models of terrace formation, and 3) collaboration between glacial and periglacial geologists in studies of glacially deformed massive ice in permafrost to interpret the origin of the ice.
Several participants expressed interest in the possibility of future workshops and field meetings on a periglacial theme. Abstracts for the present workshop are available from the convenor.